Building blue laser CNC for microfluidics, need help with beam expander /opinions

[nmz787]

see the current BOM and a rendering of some openSCAD drawings
laser etcher


thinking that this looks good for microstepping pretty fast:
Allegro MicroSystems - A4989: Dual Full-Bridge MOSFET Driver with Microstepping Translator


I need to find a 405 or 445nm laser that's 1-3 watts (higher is better so I can undercurrent and extend lifespan I think)


I'll need help with the optics too, I know I need a beam expander but I'm not sure where to start as far as lenses and powers, etc...

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[pontiacg5]

I'm not sure exactly what it is you are trying to do, but if you need a nice round laser dot you will need a lot more than a beam expander.

I'm assuming you are wanting to use the infamous 1W 445 diodes? Those lasers have a very very horrible output, it's a line more than a round dot. The only real way to fix it is with cylindrical lenses or a prism set, but both will have a bit of losses putting you further from your 1W under driven requirement.

405 diodes have a better output but they are not up to 1W+, at least reliably. I would say that around 600-700mW is all you should expect to (reliably) get from a single mode "12x" diode. You could combine a pair with a polarized beam splitter with decent results though.

But, if you are simply trying to engrave things you really have no need for a beam expander or corrective optics. Blue diode lasers are small and can handle heat well. You can simply put on on the flying head and ditch flying mirrors (and a beam expander) all together. Once you focus to a small point the horrible output pattern won't matter as much, plus it will actually engrave better.

Anyway, hope I helped a bit. If you still need more advice I know of a few forums I could point you to that know all about high power visible lasers.